With the advent of the Internet and a decline in computer prices, many people are now communicating with one another through computers or other devices interconnected by networks. A number of different communication mediums have been developed to facilitate such communications between computer users. One type of prolific communication medium is electronic mail (e-mail).
Unfortunately, because the costs of sending e-mail are relatively low, e-mail recipients are being subjected to mass, unsolicited, commercial e-mailings (colloquially known as e-mail spam or spam e-mails). Spam is akin to junk mail sent through the postal service. However, because spam e-mail requires neither paper nor postage, the costs incurred by the sender of spam e-mail are quite low when compared to the costs incurred by conventional junk mail senders. Further, senders of spam e-mail and other electronic communications may use software to generate account names and electronic communications. Due to this and other factors, e-mail and other network users are now exposed to a significant amount of spam content on a daily basis.
Spam communications impacts both service users and service providers. For service users, such as an e-mail user, spam can be disruptive, annoying, and time consuming. For a service provider, spam represents tangible costs in terms of storage and bandwidth usage. Additional costs may be incurred as network administrators work to limit and/or ban the activities of accounts that are used to send spam communications. These costs may be substantial.
Thus, particularly for large service providers, such as e-mail service providers (ESPs) and Internet service providers (ISPs), it is beneficial to stop spam before it enters the e-mail or other electronic communication system. Stopping unwanted electronic communications before they enter the system keeps down an ESP's storage and bandwidth costs and provides a better quality of service to the ESP's users. On the other hand, preventing the delivery of wanted e-mail and other electronic communications decreases the quality of service to the ESP's users, perhaps to an unacceptable degree, at least from the perspective of the users.